John Harrison and the Greatest Contest Ever

This is John Harrison, the inventor of a clock that could be used at sea.

The greatest problem of the eighteenth century was the problem of longitude.  European countries were busy making their fortunes through trade and the forefront of this great commercial enterprise was Britain.  Britain had the greatest navy in the world and the most far-flung and profitable colonies ever on the earth.   But Britain’s empire was held together by the sea and the sea was treacherous.  More sailors and ships were lost to uncharted coasts and navigational errors than could be swallowed.  The greatest obstacle to knowing with precision was the problem of longitude.

Latitude could be easily determined by shooting the sun or a star.  In fact, you can go out on any clear night and determine with precision your latitude right now using the same type of instrument that sailors from the ancient days had used.  Since the time of the Greeks, the art of navigation had hardly advanced at all.  Sailors still didn’t know where they were, and most charts were wildly inaccurate since the people making them couldn’t determine exactly where the coasts and shoals were to begin with.

John Harrison, a humble self-taught clockmaker and carpenter from a small town that was miles and miles from London thought he had the answer.  He devoted nearly his entire life to making a clock that could be taken aboard the ship and maintain accurate time.  With accurate time keeping coupled with the astronomical observations all navigators were well versed in, the exact longitude could be determined.  Great minds like Edmund Halley and Isaac Newton had worked on and failed to solve the problem.  But John Harrison had what these two were lacking, an open mind and mechanical ability.  And perhaps it was also that the previous great minds were simply too early.

A prize of 20,000 pounds had been offered by the British government to the person who solved the problem of longitude.  That is an astronomical amount for a government to offer, to the tune of more than four and a half million in today’s dollars.  Eventually, Harrison did succeed in producing a watch to match the reward conditions along with the actual trials at sea to prove it, but he only ever received a portion of the prize money.  No one was ever awarded the full prize.

This is Harrison’s famous H4 chronometer. Photo by Racklever at en.wikipedia, CC license.


Read The Longitude Prize by Joan Dash, a nonfiction book about John Harrison and the problem of longitude, written for middle-grade readers in an interesting and engaging style.


Most clocks of John Harrison’s day worked using a pendulum.  Swing a pendulum back and forth (any string with a weight on the end is a pendulum).  What happens if you yank your hand up and down or move it back and forth side to side?  Do you see the problem with pendulum-based clocks on board ship?  What other conditions aboard a ship are different from conditions on land and might cause problems for a timekeeper?  Make a list of the problems John Harrison had to overcome and how he solved them.


After you read The Longitude Prize, talk about these things:

  • What qualities did John Harrison need to achieve this great goal in his life?
  • How long did it take him to create his first accurate marine clock?  How much longer before he received the partial prize?
  • Why did Harrison spend so much time on this one project?  Do you think it was for the prize money?  If there had been no prize money would he have worked on the clock anyway?  Why?
  • How did Harrison’s family support him in his efforts?  How did other people of influence support Harrison?  Do you think he could have done it completely on his own?

Additional Layers

  • The wreck of the HMS Litchfield and the disaster of the HMS Centurion fleet are two British naval tragedies that could have been at least partially prevented by a knowledge of longitude.  Learn about these fatal voyages.
  • The voyage of Captain Cook, an exploration of the South Pacific was one of the first voyages to utilize the new marine chronometer.
  • Learn about or review longitude and latitude.
  • Brainstorm some of today’s unsolved problems in science.  Which of these inspire you?  Find out who is working on these problems.  Why do you think they are trying to solve them?

More From Layers of Learning

Every Layers of Learning has a geography section.  You will become an expert navigator of the world yourself as you dive into the geography units and explore the world in a hands-on way with your family.  Read the Curriculum Guide and then check out our catalog to see how Layers of Learning will change your homeschool forever.


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